The '262 patent provides for and teaches a conveyor system where the items being conveyed gently bump into each other. But, rather than having the physically driven belt or drive wheel slip against the item thereby necessarily generating dust or particulate matter from the slipping, the system described in the '262 patent provides for magnetic slipping of a hysteresis clutch. In one embodiment a controlled step device arrests forward motion of one item on the conveyor and the magnetic slippage occurs in the drive of the conveyor. The magnetic slipping produces no dust or particulate matter. However, successive items behind the stopped item may accumulate behind it. In practice the items being transported may be pallets, cassettes or containers carrying workpieces. In some applications the workpiece itself may be conveyed without such a carrier.
An advantage of the '262 patented system is the asynchronous or independent manner of handling the items being transported. The transportation path is segmented into sections which are independently driven. If an item on a section is stopped, the previous sections will continue to transport each successive item until there is a continuous line of items with no gaps. Items ahead of a stopped item proceed with no regard to the lined up array behind. This type of operation is in direct contrast to a continuous belt conveyor where gaps between items on the belt remain, and where stopping one item requires stopping the entire belt and therefore all the items, unless the system allows the belt to slip. However, this type of conveyor system is generally unsuitable for "clean room" conveyors. The present invention includes an alternative approach to such selective item stopping and accumulating of successive stopped items.
It is an object of the present invention to eliminate the physical bumping of successive conveyed items into each other.
It is another object of the invention to provide a further enhancement in preventing the generation of dust or particulate matter while physically moving items from station to station.
It is another object of the invention to provide a conveyor system wherein various items are selectively stopped and started along the conveyor path and selectively stopped and accumulated in a controlled fashion.
It is yet another object of the invention to provide a conveyor system with intrinsic controls as well as external automatic or manual controls. A related object of the invention is to provide a system wherein the item locations are controlled either locally, with controls related to each of the successive sections of the conveyor path communicating with each other, or universally, wherein controls related to all sections of the conveyor path communicating with each other directly or via a universal server.